Co-reporter:Zhiwei Lin;Yangfan Sun
The International Journal of Advanced Manufacturing Technology 2017 Volume 92( Issue 5-8) pp:2325-2339
Publication Date(Web):31 March 2017
DOI:10.1007/s00170-017-0247-8
Toolpath planning for irregular-shaped compound freeform surfaces remains a challenge. This work presents a new approach for compound surface finishing by treating the toolpath planning task as a traveling salesman problem (TSP). The concept of curvature map is proposed. With this concept, the curvatures of the surface patches are recorded to corresponding cells of the map and then the path intervals are determined. The CC points as well as the normal vectors are calculated on the mesh model of the compound surface with a linear algorithm. The obtained CC points are linked as cities in LKH, in which the distance function is redefined to cope with the illegal linking problems. With LKH, tool retractions are no longer necessary. The resulted toolpath is capable of covering the whole compound surface with only one pass. The proposed toolpath generation method is more forgiving on the input. It does not require the surfaces to be perfectly conform on the joining boundaries. Several compound surface examples have been used to verify the feasibility of the proposed method.
Co-reporter:Yong He, Wen-bin Wu and Jian-zhong Fu
RSC Advances 2015 vol. 5(Issue 4) pp:2694-2701
Publication Date(Web):05 Dec 2014
DOI:10.1039/C4RA12165A
In this study, we developed a novel and facile method for fabricating paper-based microfluidic analytical devices (μPADs) with dynamic mask photo curing (DMPC), generated by a desktop stereolithography (SL) three-dimensional printer (3DP). First, we immersed the filter paper in ultraviolet (UV) resin to cover it evenly. Next, we exposed it to UV-light through a dynamic mask of the negative channel pattern. After curing, the UV-exposed regions become highly hydrophobic, creating hydrophobic barriers. Finally, we washed the uncured resin with anhydrous alcohol and fine μPADs were obtained. The resolution of the fabricated hydrophilic channels was 367 ± 20 μm, with a between-channel hydrophobic barrier of 400 ± 21 μm. To verify this method's performance, we fabricated μPADs with DMPC for quantitative analysis of nitrite ion. This new method represents a leap forward in terms of time saved. Since all hydrophobic barriers are cured at a time, the fabrication process can be completed in only two minutes, no matter how complex the patterns are. Compared to the widely used fabrication method of μPADs, wax printing, DMPC provides an alternative way to fabricate μPAD with different hydrophobic barriers materials, which provides the possibility of designing different μPADs according to the application environments.
Co-reporter:Yong He, WenBin Wu, Ting Zhang and JianZhong Fu
RSC Advances 2015 vol. 5(Issue 49) pp:39138-39144
Publication Date(Web):23 Apr 2015
DOI:10.1039/C5RA01410G
A facile hot embossing method—low pressure hot embossing (LPHE)—is reported in this paper. Compared with large and expensive hot embossing machines, just an oven is used for heating with a compact self-designed loading device inside to apply pressure. Due to the small loading device, only a low embossing pressure can be applied. Micro linear arrays were successfully fabricated with this method and the embossing process was systemically investigated. Orthogonal arrays were used to analyze the hot embossing behavior under a low embossing pressure. As LPHE is easy to realize at a cheap price, it is very helpful for researchers interested in fabricating micro structures such as micro fluidic chips used in prototype experiments.
Co-reporter:Yong He, Yan Wu, Jian-Zhong Fu and Wen-Bin Wu
RSC Advances 2015 vol. 5(Issue 95) pp:78109-78127
Publication Date(Web):07 Sep 2015
DOI:10.1039/C5RA09188H
When compared with conventional microfluidic chips made of glass and polymer substrates, paper-based microfluidic analysis devices (μPADs) possess many unique advantages, including low-cost, easy-to-fabricate, strong capillary action and good biological compatibility. In recent years, μPADs have attracted increased interest and attention, which has led to their rapid development. Thousands of literature reports regarding μPADs have been published and a variety of μPADs fabrication methods have been reported. This review focuses on the development of the fabrication methods of 2D and 3D μPADs since 2007. A summary of the advantages and disadvantages of these methods is provided with particular attention paid to the resolution and cost of each method. Suitable applications of each method are discussed. Also, some trends of μPADs are summarized.
Co-reporter:Jintao Lai;Hongyao Shen
International Journal of Precision Engineering and Manufacturing 2015 Volume 16( Issue 3) pp:433-439
Publication Date(Web):2015 March
DOI:10.1007/s12541-015-0059-4
A new method for machining error inspection of T-spline surface by on-machine measurement (OMM) is investigated in this study. With the presented method, a relatively small number of sampling points are needed to evaluate the machining error of the surface. The sampling strategy based on the dominant of the control vertex is proposed. Based on the inspection data, the machined surface can be obtained through a T-spline surface reconstruction algorithm. Verification experiments showed that the inspection error between the OMM method and the coordinate measuring machine (CMM) method is within 13.3%. Simulation results shows that the fitting error in critical area can be improved with less additional sampling points while the surface is presented in T-spline surface.
Co-reporter:Peng Zhao;Yiyan Peng;Weimin Yang;Lih-Sheng Turng
Journal of Polymer Science Part B: Polymer Physics 2015 Volume 53( Issue 10) pp:700-708
Publication Date(Web):
DOI:10.1002/polb.23691
ABSTRACT
Crystallization has significant effects on the physical and mechanical properties of polymer products; therefore, crystallization measurements are important for understanding and predicting polymer products' properties. However, traditional crystallization measurement methods have disadvantages in practical applications because they can be destructive, offline, unsafe, and expensive. Recently, ultrasonic technology has shown great potential as a nondestructive, online, real-time, and environmentally friendly measurement method for polymer characterization. In this study, a novel measurement method based on ultrasonic technology was proposed to study the crystallization characteristics of poly(lactic acid) (PLA) parts. An annealing process was employed to produce PLA parts with different degrees of crystallinity. A new ultrasonic water immersion method was used to measure the ultrasonic velocities of these annealed PLA parts. It has been found that the plot of the inverse ultrasonic velocity versus the degree of crystallinity shows good linearity over the whole crystallinity range for all three annealing temperatures. The linear relationship between the inverse of the ultrasonic velocity and the crystallinity observed in this study could provide a nondestructive method for investigating the degree of crystallinity of polymers, which can be implemented both offline and online. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 700–708
Co-reporter:Yong He;Jingjiang Qiu;Jiong Zhang
Microfluidics and Nanofluidics 2015 Volume 19( Issue 2) pp:447-456
Publication Date(Web):2015 August
DOI:10.1007/s10404-015-1571-7
This study demonstrated how to quickly and effectively print two-dimensional (2D) and three-dimensional (3D) microfluidic chips with a low-cost 3D sugar printer. The sugar printer was modified from a desktop 3D printer by redesigning the extruder, so the melting sugar could be extruded with pneumatic driving. Sacrificial sugar lines were first printed on a base layer followed by casting polydimethylsiloxane (PDMS) onto the layer and repeating. Microchannels were then printed in the PDMS solvent, microfluidic chips dropped into hot water to dissolve the sugar lines after the PDMS was solidified, and the microfluidic chips did not need further sealing. Different types of sugar utilized for printing material were studied with results indicating that maltitol exhibited a stable flow property compared with other sugars such as caramel or sucrose. Low cost is a significant advantage of this type of sugar printer as the machine may be purchased for only approximately $800. Additionally, as demonstrated in this study, the printed 3D microfluidic chip is a useful tool utilized for cell culture, thus proving the 3D printer is a powerful tool for medical/biological research.
Co-reporter:Chen-hui Xia;Jian-zhong Fu;Yue-tong Xu
Journal of Zhejiang University-SCIENCE A 2014 Volume 15( Issue 10) pp:761-773
Publication Date(Web):2014 October
DOI:10.1631/jzus.A1400074
A novel method is presented for fast identification of a machine tool selected point temperature rise, based on an adaptive unscented Kalman filter. The major advantage of the method is its ability to predict the selected point temperature rise in a short period of measuring time, like 30 min, instead of 3 to 6 h in conventional temperature rise tests. A fast identification algorithm is proposed to predict the selected point temperature rise and the steady-state temperature. An adaptive law is applied to adjust parameters dynamically by the actual measured temperature, which can effectively avoid the failure of prediction. A vertical machining center was used to validate the effectiveness of the presented method. Taking any selected point, we could identify the temperature rise at that point in 28 min. However, if the method was not used, it took 394 min to obtain the temperature rise curve from the start-up of the machine tool to the time when it reached a steady-state temperature. The root mean square error (RMSE) between the estimated and measured temperatures in the period of 394 min was 0.1291 °C, and the error between the estimated and measured steady-state temperatures was 0.097 °C. Therefore, this method can effectively and quickly identify a machine tool selected point temperature rise.为了缩短机床温升试验时间, 提出一种机床热特性快速辨识方法, 利用较短时间的温度采样数据即可准确预测出完整的温升曲线, 进而获得热平衡时间及稳态温度等热特性参数。提出了基于自适应无味卡尔曼滤波的机床选点温升快速辨识方法, 其中最短辨识时间判据可以有效解决如何寻找准确辨识热特性参数的最短采样时间问题, 而自适应无味卡尔曼滤波则可以实时调整参数, 防止外界因素对辨识的干扰。由于无味卡尔曼滤波在非线性状态预测和参数辨识上具有优势, 所以本文将无味卡尔曼滤波算法应用到机床选点温升辨识上。 为了防止辨识过程中的发散退化等问题, 将无味卡尔曼滤波发展为自适应无味卡尔曼滤波(图1)。 在快速辨识方法上提出了最短辨识时间判据(图2)。 文章中又将此算法应用到实际的立式加工中心温升辨识上, 证明了该算法的可行性及有效性(图5 和6)。 最后又将带有自适应调整过程的无味卡尔曼滤波算法和不带调整过程的算法做了对比, 显示了自适应调整过程对辨识算法的重要性(图6 和11)。基于自适应无味卡尔曼滤波的机床选点温升快速辨识方法可以准确快速地辨识出温升曲线, 获取热特性参数, 将原来394 min 的热平衡试验时间缩短, 只需28 min 即可得到温升变化情况。
Co-reporter:Guoqiang Fu;Yuetong Xu
The International Journal of Advanced Manufacturing Technology 2014 Volume 71( Issue 9-12) pp:1653-1667
Publication Date(Web):2014 April
DOI:10.1007/s00170-013-5586-5
This paper proposes a product of exponential (POE) model to integrate the geometric errors of multi-axis machine tools. Firstly, three twists are established to represent the six basic error components of each axis in an original way according to the geometric definition of the errors and twists. The three twists represent the basic errors in x, y, and z directions, respectively. One error POE model is established to integrate the three twists. This error POE formula is homogeneous and can express the geometric meaning of the basic errors, which is precise enough to improve the accuracy of the geometric error model. Secondly, squareness errors are taken into account using POE method to make the POE model of geometric errors more systematic. Two methods are proposed to obtain the POE models of squareness errors according to their geometric properties: The first method bases on the geometric definition of errors to obtain the twists directly; the other method uses the adjoint matrix through coordinate system transformation. Moreover, the topological structure of the machine tools is introduced into the POE method to make the POE model more reasonable and accurate. It can organize the obtained 14 twists and eight POE models of the three-axis machine tools. According to the order of these POE models multiplications, the integrated POE model of geometric errors is established. Finally, the experiments have been conducted on an MV-5A three-axis vertical machining center to verify the model. The results show that the integrated POE model is effective and precise enough. The error field of machine tool is obtained according to the error model, which is significant for the error prediction and compensation.
Co-reporter:Peng Zhao;Huamin Zhou;Yong He;Kan Cai
The International Journal of Advanced Manufacturing Technology 2014 Volume 72( Issue 5-8) pp:765-777
Publication Date(Web):2014 May
DOI:10.1007/s00170-014-5711-0
Nondestructive online monitoring of injection molding processes is of great importance. However, almost all prior research has focused on monitoring polymers in molds and damaging the molds. Injection molding machines are the most important type of equipment for producing polymeric products, and abundant information about actual polymer processing conditions can be obtained from data collected from operating machines. In this paper, we propose a nondestructive online method for monitoring injection molding processes by collecting and analyzing signals from injection molding machines. Electrical sensors installed in the injection molding machine, not in the mold, are used to collect physical signals. A multimedia timer technique and a multithread method are adopted for real-time large-capacity data collection. An algorithm automatically identifies the different stages of the molding process for signal analysis. Moreover, ultrasonic monitoring technology is integrated to measure the cavity pressures. Experimental results show that our nondestructive method can continuously monitor the injection molding process in real time and automatically identify the different stages of the molding process. The packing parameters, including the filling-to-packing switchover point and the packing time, can be optimized based on these data. Furthermore, the ultrasonic reflection coefficient and the actual cavity pressure have similar trends, and our technique for measuring the cavity pressure is accurate and effective.
Co-reporter:Zhiwei Lin;Hongyao Shen
The International Journal of Advanced Manufacturing Technology 2014 Volume 74( Issue 1-4) pp:187-197
Publication Date(Web):2014 September
DOI:10.1007/s00170-014-5981-6
Nonlinear errors in five-axis machining process are caused due to the nonlinear motions of the rotational axes, which are inevitable. For the RT-type machine tool, the workpiece setup location on the working table has a direct effect on the nonlinear errors, thus there must be an optimal setup position which can reduce the nonlinear errors. Today’s five-axis machine tools are mostly equipped the with the RTCP (rotational tool center point) function, with which the NC program becomes independent from the workpiece setup. In this paper, we have focused on finding the optimal workpiece setup for the RT-type machine tool with RTCP function, more specifically, the Mikron UCP 600 five-axis machine tool in our lab. The kinematics of the machine tool is briefly analyzed. Based on that, the nonlinear error evaluation method with RTCP interpolation is derived. With this method, nonlinear errors can actually be considered as a function of the workpiece setup position. Then, the particle swarm optimization (PSO) is applied to find the optimal workpiece setup, in which a mutation operation is used since PSO traps into local optimum easily. The proposed optimal workpiece setup method is implemented and tested. Example results show that the optimal setup with least nonlinear errors can be found. Some interesting results also show that the nonlinear errors are not sensitive with the z component of the workpiece setup vector. The proposed optimization is nearly zero-cost and easy to both understand and implement, yet has a potential to reduce the nonlinear errors and thus to improve the accuracy of five-axis machining.
Co-reporter:Ya Zhang;Zichen Chen
Chinese Journal of Mechanical Engineering 2014 Volume 27( Issue 5) pp:999-1007
Publication Date(Web):2014/09/01
DOI:10.3901/CJME.2014.0611.108
Compared with the traditional non-cutting measurement, machining tests can more accurately reflect the kinematic errors of five-axis machine tools in the actual machining process for the users. However, measurement and calculation of the machining tests in the literature are quite difficult and time-consuming. A new method of the machining tests for the trunnion axis of five-axis machine tool is proposed. Firstly, a simple mathematical model of the cradle-type five-axis machine tool was established by optimizing the coordinate system settings based on robot kinematics. Then, the machining tests based on error-sensitive directions were proposed to identify the kinematic errors of the trunnion axis of cradle-type five-axis machine tool. By adopting the error-sensitive vectors in the matrix calculation, the functional relationship equations between the machining errors of the test piece in the error-sensitive directions and the kinematic errors of C-axis and A-axis of five-axis machine tool rotary table was established based on the model of the kinematic errors. According to our previous work, the kinematic errors of C-axis can be treated as the known quantities, and the kinematic errors of A-axis can be obtained from the equations. This method was tested in Mikron UCP600 vertical machining center. The machining errors in the error-sensitive directions can be obtained by CMM inspection from the finished test piece to identify the kinematic errors of five-axis machine tool trunnion axis. Experimental results demonstrated that the proposed method can reduce the complexity, cost, and the time consumed substantially, and has a wider applicability. This paper proposes a new method of the machining tests for the trunnion axis of five-axis machine tool.
Co-reporter:Chenhui Xia;Yuetong Xu
The International Journal of Advanced Manufacturing Technology 2014 Volume 70( Issue 1-4) pp:19-31
Publication Date(Web):2014 January
DOI:10.1007/s00170-013-5239-8
A new method to fast identify machine tool selected point temperature rise is presented. Based on operational thermal modal analysis, a temperature rise curve of each machine tool selected point can be obtained, and thermal equilibrium time and steady-state temperature can be calculated based on the measured temperature data during a short time of a warm-up run. The major advantage of this approach is to predict selected point temperature rise of the machine tool in the short test period of time like half an hour instead of 3 to 6-h running test in practice. A spindle system model is analyzed in ANSYS software, and the simulation temperature data of several selected points are treated as the measured temperature. By dealing with the assuming measurement temperature based on the new method, the effectiveness of the method is verified and how to get the minimal time for identification is also illustrated. At last, the temperature rise test in the vertical machining center has been done. The temperature rise of the selected point has been identified in 26.35 min while the time of obtaining the temperature rise curve from the start-up of machine tool to the temperature steady-state machine tool reaching in practice is 320 min. The root mean squared error (RMSE) between the estimated and measured temperature is 0.107 °C, and the error between the estimated and measured steady-state temperature is 0.155 °C. So this method is proven to be effective and quick for identifying the machine tool selected point temperature rise. Furthermore, it has universal applicability due to the validation in the different spindles.
Co-reporter:Wen-feng Gan;Jian-zhong Fu;Hong-yao Shen
Journal of Zhejiang University-SCIENCE A 2014 Volume 15( Issue 3) pp:157-171
Publication Date(Web):2014 March
DOI:10.1631/jzus.A1300274
In this work, a novel morphing machining strategy (MMS) is proposed. In the method, the workpiece is progressively carved out from the stock. Pitfalls in conventional iso-height strategy, such as sharp edges and unevenly distributed left-over materials, are overcome. Moreover, to calculate different levels in the MMS, an energy-based morphing algorithm is proposed. Finally, the proposed strategy is employed in the machining of artificial bone represented by a T-spline surface. The excellent properties of T-spline, such as expressing complex shapes with a single surface, have been well adopted to artificial bone fabrication. Computer simulation and the actual machining of the middle finger bone show the feasibility of the proposed strategy.
Co-reporter:Peng Zhao, Shuo Wang, Ji Ying, Jianzhong Fu
Polymer Testing 2013 Volume 32(Issue 8) pp:1436-1444
Publication Date(Web):December 2013
DOI:10.1016/j.polymertesting.2013.09.006
Non-destructive measurement of the cavity pressure is of great importance for monitoring, optimizing and controlling the injection molding process. However, to date, almost all researches have relied on embedded pressure probes, and holes have to be drilled in the molds. In this paper, a non-destructive cavity pressure measurement method is proposed based on ultrasonic technology and a Gaussian process. According to the pressure-volume-temperature profile, the cavity pressure of a given polymer can be treated as a function of the density and the temperature. Moreover, the cavity pressure is significantly affected by injection hydro-cylinder pressure. Ultrasonic technology is employed to detect the variation of polymer density during injection molding. The Gaussian process is adopted to model the functional relationships between the cavity pressure, the ultrasonic signal, the mold temperature and the injection hydro-cylinder pressure. Experimental results show that the proposed Gaussian process regression model has a better modeling performance than that of the neural network regression model, and the proposed measurement method is capable of measuring the cavity pressure at different processing conditions and measurement locations during injection molding. In general, the proposed method offers several advantages: (1) non-destructive, (2) flexible, (3) no wires, (4) low-cost, and (5) health and safety, so it has great application prospects in injection molding.
Co-reporter:Yong He;Peng Zhao ;Zi Chen Chen
Polymer Engineering & Science 2013 Volume 53( Issue 6) pp:1314-1320
Publication Date(Web):
DOI:10.1002/pen.23379
Abstract
Low filling efficiency and large thermal stress are two important problems that limit the wide use of hot embossing especially in fabricating high aspect ratio patterns. Two types of flow barriers, the first being an accessorial slot on the mold (SFB), the other was a block on the hot embossing machine (BFB), were designed to enhance polymer filling and their performances were simulated with the finite element method. The numerical simulation results show that two kinds of flow barriers can also accelerate the polymer filling speed and improve filling efficiency. The BFB has a better promoting effect and can be easily used as a quasi close-die embossing process. The shrinkage of the polymer and mold is made uniform with a designed polymer grip holder to minimize the thermal stress. The polymer was clipped at a temperature in a cooling step and its deformation was fixed; thus, the shrinkage of the polymer can be equal to the mold at a special temperature. An improved hot embossing machine was designed and the hot embossing process was modified to satisfy these requirements. At last successful fabrication of the light guide plate verified the improvements. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Co-reporter:Yong He;Jian-Zhong Fu;Zi-Chen Chen
Microsystem Technologies 2009 Volume 15( Issue 7) pp:963-968
Publication Date(Web):2009 July
DOI:10.1007/s00542-009-0858-6
The pattern height of hot embossing was analyzed based on the polymer power–law material assumption for better controlling product quality. The time development of the polymer substrate height, pattern height and the imprint pressure were obtained. The imprint temperature with respect to the pattern height was discussed. Theory analysis shows that in a constant imprint pressure, the pattern height has a power relationship with the imprint time. At the beginning imprint stage, as for the elastic response of polymer, the pattern height increases rapidly. With the time increasing, the polymer deform is mainly caused by creep and this results in low imprint speed. On the other hand, the increasing friction force between the polymer and the mold will further reduce the imprint speed. The theoretical data were compared with experiments and the results show that this model can well predict the rule of polymer substrate thickness variation.
Co-reporter:Kun Ren;Jian-zhong Fu;Zi-chen Chen
Journal of Zhejiang University-SCIENCE A 2007 Volume 8( Issue 12) pp:1938-1943
Publication Date(Web):2007 November
DOI:10.1631/jzus.2007.A1938
To reduce mechanical vibrations induced by big errors compensation, a new software compensation method based on an improved digital differential analyzer (DDA) interpolator for static and quasi-static errors of machine tools is proposed. Based on principle of traditional DDA interpolator, a DDA interpolator is divided into command generator and command analyzer. There are three types of errors, considering the difference of positions between compensation points and interpolation segments. According to the classification, errors are distributed evenly in data processing and compensated to certain interpolation segments in machining. On-line implementation results show that the proposed approach greatly improves positioning accuracy of computer numerical control (CNC) machine tools.
Co-reporter:Zhiwei Lin, Jianzhong Fu, Hongyao Shen, Guanhua Xu, Yangfan Sun
International Journal of Machine Tools and Manufacture (September 2016) Volume 108() pp:1-12
Publication Date(Web):1 September 2016
DOI:10.1016/j.ijmachtools.2016.05.006
•The machined surface textures in avoiding five-axis singular problem are concerned.•The ATOR concept together with the non-singular ATOR is proposed.•The surface texture of the tool axis picked inside ATOR is acceptable.•The orientation curve is re-generated with a B-spline curve interpolation schema.The singular phenomenon is common in five-axis machining process. Most of the existing methods try to solve the problem by deforming the tool orientations or inserting extra cutter locations after the tool path is generated, with the drawbacks that (1) the machining geometry errors are not respected and (2) irregular machined surface textures might be caused. This paper dedicates to improve the machined surface textures in the scenario of avoiding the five-axis singularities. In this paper, the acceptable-texture orientation region (ATOR) concept is proposed. If the tool orientation is picked inside the ATOR, the resulted surface texture is considered to be acceptable. Based on this concept, the tool orientations are optimized locally. For a given tool path, if the orientation curve crosses the singular circle, it is locally modified out of the circle with a bridge point locating schema and a cubic B-spline interpolation technique. Eventually, the obtained new orientation curve goes around the singular circle like a rubber band to avoid the singular problem and remains unmodified to achieve the best machined surface qualities for the rest pieces. As the process is implemented at the tool path planning stage, the machining geometry errors can also be respected.
Co-reporter:Zhiwei Lin, Jianzhong Fu, Xinhua Yao, Yangfan Sun
International Journal of Machine Tools and Manufacture (November 2015) Volume 98() pp:41-49
Publication Date(Web):1 November 2015
DOI:10.1016/j.ijmachtools.2015.09.001
•A tool orientation translation method is developed to avoid the five-axis singularities.•The mechanism of irregular machined surface textures is analyzed.•The tool orientation changes are controlled by an intelligent optimization algorithm.•The machined surface textures are greatly improved.This paper looks into the irregular machined surface textures appearing in the process of avoiding five-axis singularities using the C-space based tool orientation translation method. At first, the mechanism for the appearances of the irregular surface textures is analyzed. A cutting simulation in VERICUT reveals that irregular surface textures are actually caused by lacking control of the tool orientation angles in the orientation modification process. Realizing that, a modified particle swarm optimization (PSO) is intergraded into the previous tool orientation translation method. In the PSO, the particle evolving equations are redefined and a mutation operation is added. The objective of the PSO is to find an optimal translating vector in the C-space so that the changed tool orientation angles can reach minimum values. In this way, the surface textures can be controlled. Three comparative cutting experiments with fillet endmills are carried out to verify the effect of the proposed method. The experimental results show that: (1) with the tool orientation translation method, the five-axis singular problem can be well avoided; and (2) with the optimal translating vector found by the PSO, the machined surface textures can be greatly improved.
Co-reporter:Zhiwei Lin, Jianzhong Fu, Hongyao Shen, Wenfeng Gan
Computer-Aided Design (November 2014) Volume 56() pp:120-132
Publication Date(Web):1 November 2014
DOI:10.1016/j.cad.2014.06.010
•Uniform scallop tool path has been generated via cutting simulation.•Grass/CC rings are calculated both in parametric and 3D Euclidean space.•Optimized methods are used to fast calculate the grass/CC ring.•The method is free of local geometry assumptions; thus is more precise.•The method is generic for any cutter, parametric surface and tool path pattern.In this paper, a generic uniform scallop tool path generation method for five-axis machining is presented. Unlike the conventional methods which are based on the local surface geometry assumptions, this method is inspired by cutting simulation. Initially, the designed surface is planted with dense grasses. If a cutter is put onto the surface, the affected grasses will be cut short. All the affected grasses form a grass ring on the surface. When the cutter moves along the previous tool path, the envelope of the grass rings will form a machining band. Based on the machining band, cutter contact points can be found on the surface to ensure that the cutting edge touches exactly on the side of the band. These cutter contact points are fitted to construct the next tool path. In this way, all the tool paths can be generated recursively. An optimization is also developed to improve the computing efficiency of the path generation process. The proposed uniform scallop tool path generation method is generic. It can be popularized to (1) any kind of end mill with various sizes, (2) any kind of parametric surface and (3) directional- or contour-parallel tool path topologies. Another salient feature of this method is that it is free of local surface geometry assumptions, so the obtained tool paths are more precise. The proposed method is implemented and evaluated with several freeform surface examples. The feasibility of the method is also verified by actual cutting experiment.
Co-reporter:Wen-Feng Gan, Jian-Zhong Fu, Hong-Yao Shen, Zhi-Yu Chen, Zhi-Wei Lin
Computer-Aided Design (July 2014) Volume 52() pp:51-63
Publication Date(Web):1 July 2014
DOI:10.1016/j.cad.2014.02.013
•Introducing T-spline surface to CAM area.•Improved space-filling curve (ISFC) tool path for T-spline surfaces machining.•ISFC generates a non-retracted tool path.•Tool path planning algorithm for irregular boundaries and holes in pre-image.•Compensation path algorithm to avoid uncut materials on tool path corners.Because of its flexible topology and robust data structure, the T-spline surface has become the trend of free-form surfaces representation in the realm of CAD design, animation and CAE. Yet its application in manufacturing has not been fully explored. In this work, the possibility of direct tool path generation on the T-spline surface has been discussed. An improved space-filling curve (ISFC) tool path planning algorithm has been proposed to exploit the advantage of T-spline as a mathematical representation of free-form surfaces in CAM process, as well as to overcome its disadvantages such as irregular boundaries and holes in the pre-image. The turning problem in traditional SFC has been tackled using Hermite compensation curves. Finally, a prototype system has been developed to implement the proposed algorithm and actual machining has been conducted. The result shows the feasibility as well as the efficiency of the proposed method for T-spline surfaces tool path generation compared to commercial CAM system.
Co-reporter:Zhenya He, Jianzhong Fu, Liangchi Zhang, Xinhua Yao
International Journal of Machine Tools and Manufacture (January 2015) Volume 88() pp:1-8
Publication Date(Web):1 January 2015
DOI:10.1016/j.ijmachtools.2014.07.009
•All the six error parameters inherent to a rotation axis can be identified.•Only the measured axis is moving during the measurement process.•The error identification does not need a volumetric error modeling.•The identified process, a simple algebraic process, is easier to understand.This paper presents a new error measurement method, a Dual Optical Path Measurement Method (DOPMM), to identify error parameters of the rotational axis of a machine tool along its error sensitive directions. The method development was carried out on a motorized rotary stage equipped with a Doppler laser instrument. An error measurement experiment and a machining experiment were conducted on a five-axis machining center with a titling rotary table. It was found that the DOPMM can identify all of the six volumetric error parameters with the simple algebraic operations. Compared with the existing ball bar tests, which need a mathematical error modeling of machine tools to separate the error parameters, the identified process of DOPMM is more simple and easier to understand. And the operation of machine tools during the measurement is much easier than that of the existing ball bar tests. The experimental results showed that the part precision can have a significant improvement of 68% when the identified error parameters are used for error compensation. Hence, the measurement method established in this study is sensible and efficient, and could be used for the error compensation on a wide range of machine tools to improve their machining precision.
Co-reporter:Guoqiang Fu, Jianzhong Fu, Yuetong Xu, Zichen Chen, Jintao Lai
International Journal of Machine Tools and Manufacture (February 2015) Volume 89() pp:170-181
Publication Date(Web):1 February 2015
DOI:10.1016/j.ijmachtools.2014.11.005
•Contribution of each axis to errors of tool is obtained with differential motion matrix.•The summation of contributions is integrated error components of tool.•Constructed Jacobian reuses the differential motion matrix for compensation.•Six-circle method is proposed to identify ten errors of each rotary axis.•Experimental demonstration is presented to verify the accuracy improvement.This paper presents the precision enhancement of five-axis machine tools according to differential motion matrix, including geometric error modeling, identification and compensation. Differential motion matrix describes the relationship between transforming differential changes of coordinate frames. Firstly, differential motion matrix of each axis relative to tool is established based on homogenous transformation matrix of tool relative to each axis. Secondly, the influences of errors of each axis on accuracy of tool are calculated with error vector of each axis. The sum of these influences is integration of error components of machine tool in coordinate system of tool. It endows the error modeling clear physical meaning. Moreover, integrated error components are transformed to coordinate frame of working table for integrated error transformation matrix of machine tools. Thirdly, constructed Jacobian is established using differential motion matrix of each axis without extra calculation to compensate the integrated error components of tool. It makes compensation easy and convenient with reuse of intermediate. Fourthly, six-circle method of ballbar is developed based on differential motion matrix to identify all ten error components of each rotary axis. Finally, the experiments are carried out on SmartCNC500 five-axis machine tool to testify the effectiveness of proposed accuracy enhancement with differential motion matrix.
Co-reporter:Zhiwei Lin, Jianzhong Fu, Hongyao Shen, Wenfeng Gan, Shuhua Yue
Computer-Aided Design (December 2015) Volume 69() pp:51-61
Publication Date(Web):1 December 2015
DOI:10.1016/j.cad.2015.07.002
•A new way of planning SFC type tool path is proposed.•Cutting simulation method is proposed to evaluate the scallop error.•Tool path planning task is formulated as a TSP and LKH is applied for solution.•In LKH, the distance function is redefined to avoid incorrect linking problem.In freeform surface finishing, there are three major types of tool path topologies: the direction-parallel type, the contour–parallel type and the space-filling curve (SFC) type. The SFC topology is capable of covering the whole surface with only one path. In this paper, we present a new way of planning the SFC type tool path by formulating the planning task as a traveling salesman problem (TSP). The optimal path is generated in two steps. Firstly, a set of regular cutter contact (CC) points is generated on the input surface. A cutting simulation method is developed to evaluate the scallop error and determine the position of the next CC point in cross-feed direction. This method is free of local surface curvature assumptions and is therefore accurate for big cutters. Secondly, the obtained CC points are input into an efficient TSP solver LHK for the optimal CC point linking sequences. To stop the CC points from diagonal linking or penetrating linking, the Euclidean distance evaluation function for two CC points is redefined in LHK. The proposed tool path generation method is verified with several freeform surface examples; the results show that the method can automatically find the optimal feed direction and it can generate shorter tool path than the traditional SFC method. The feasibility of the proposed method is also verified by a cutting experiment.
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